Reviewed by
Liang Chen
School of Architecture, The Chinese University of Hong Kong
The modelling of pedestrian dynamics has long been one of the key objectives for transportation research and human movement-related studies in social science. Modelling the pattern of pedestrian flow, especially in cities, is a complex issue in that it involves the impact of built environment on human’s individual movement. This seminal book by Emiliano Cristiani, Benedetto Piccoli and Andrea Torsin provides the theoretical foundations for the modelling of pedestrian dynamics with a focus on the mathematical basis of the principles of movement, and simple simulation cases are also provided as a proof of concept.The book is organised in two parts. Part I serves mainly as a brief introduction which aims to cover various features of pedestrian movement (what can be modelled) and illustrates how these features can be depicted through simulations (what simulation can do). Both real-world photos and virtual parametric simulations are presented to show the pattern of pedestrian flow. Part I is far from a comprehensive introduction into pedestrian motion phenology or an in-depth literature review of pedestrian dynamic modelling. This is understandable, as pedestrian motion is by its virtue subjective action influenced by various factors, and the research work in the field is massive and still growing fast, and a comprehensive introduction of pedestrian movement with detailed review will make Part I overly long and deviating.
Part II, which is the essence of this book, discusses the mathematical approaches to the modelling of pedestrian dynamics. Equations, diagrams and algorithms are developed to characterise the behavioural aspects of pedestrian movement. Both microscopic and macroscopic scales are covered. Emphasis is given to measurement-based models which are built on the foundation of probability theory. Both numerical approximation and analytical reasoning approaches are taken to solve the equations that describe the velocity of pedestrians and their interactions. Chapter 5 presents the core content of the book, which is multiscale modelling of pedestrian dynamics. However, how different scales are connected is not explicitly discussed. For example, the discrete choice model mainly deals with the purpose of a pedestrian’s trip. On the other hand the social force model deals with a pedestrian’s actual movement in space and with interactions with others. From a top-down perspective the levels of work include the perceptual aspect, behavioural aspect and reactive aspect. In this sense the logical circle from a pedestrian’s perception of the surrounding environment to its physical movement is yet to be developed.
With the book’s focus on the mathematical foundations of pedestrian dynamics it comes with both strengths and drawbacks. One of the benefits is that equations and models delineate the detailed mechanisms of the revealed patterns of pedestrian movement. On the other hand, from the view point of a practitioner, urban context and real world settings are insufficiently incorporated by this mathematical approach, and how the models work is too abstract. As a result the test cases are still more like in-lab experiments rather than real world applications.
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